Of methods of detecting coating defect parts on a buried pipeline, a Direct Current Voltage Gradient (DCVG) technique, which is known as a method having the highest precision, is adapted to discover the coating detect parts by detecting the deformation of a potential distribution appearing on the soil around the coating defect parts at the time of detecting the coating defect parts, which may result from mechanical defects during the burying of the pipeline, or damages caused by other constructions. A Closed Interval Potential Survey (CIPS) method is adapted to survey the corrosion protection and coating states of a buried pipeline by connecting a measurement wire to a lead wire of the buried pipeline and measuring the potential of a portion immediately above the pipeline while moving a reference electrode along the buried pipeline at regular intervals (several meters). The DCVG and the CIPS methods are performed while a rectifier for corrosion protection is switched on/off to the buried pipeline.
For an apparatus for measuring data using the above two methods, that is, the DCVG and CIPS methods, there has been used an Electric Pen Recorder (EPR), which is a device for recording, using a pen, continuously measured values on a paper in the form of analog data. In the prior art, an operation is performed in such a way that an operator determines accurate values by reading contents measured in a field with the naked eye using the EPR, records the accurate values using a writing tool, returns to an office, and arrange the measured values.
Recently, besides the apparatus using the EPR, apparatuses for converting values measured in a field into digital data, and then arranging and displaying the digital data have been developed. However, such apparatuses are problematic in that, since they employ small-sized Liquid Crystal Display (LCD) panels, the apparatuses cannot display continuously measured values on the LCD panels, and, additionally, it cannot display previously measured values in the form of accumulative data.